A molecular systematic framework for equine strongyles based on ribosomal DNA sequence data

In this study, molecular data sets were used to address the controversies relating to the systematics of strongyloid nematodes of equids utilising morphological data sets. DNA sequences of the first and second internal transcribed spacers (ITS-1 and ITS-2) of ribosomal DNA were determined for 30 species of equine strongyles and the systematic relationships reconstructed using phenetic and phylogenetic tree-building methods. The molecular data provided support for the hypothesis that the genera with large subglobular buccal capsules are ancestral to those with small cylindrical buccal capsules, but did not provide support for the current division of the subfamilies Strongylinae and Cyathostominae or for some taxonomic groupings (i.e. generic designations of species) within the Cyathostominea based on morphological data. Although not entirely concordant, the current molecular data provide a systematic framework for future studies of equine strongyles, which could be exploited in combination with new, phylogenetically informative morphological data sets.